DESCRIPTION: (Applicant's Description) Dietary antioxidants may protect cigarette smokers from the initiating events in chemical carcinogenesis. To test this hypothesis, we are currently carrying out a study using biological markers as intermediate endpoints to test the efficacy of an antioxidant vitamin intervention in 100 heavy smokers. After a one month run-in period, eligible, compliant subjects are randomly assigned to one of two treatment groups: 1, 500 mg vitamin C, 12 mg -carotene and 400 IU vitamin E (a-tocopherol) per day and 11, placebo. Blood, buccal cells and urine samples are being collected upon enrollment and at 1, 3, and 6 months. Funds are currently available for analysis of: 1) polycyclic aromatic hydrocarbon (PAH)-DNA adducts in mononuclear cells by a competitive enzyme-linked immunosorbent assay (ELISA) using a polyclonal antiserum which recognizes benzo(a)pyrene and structurally related PAH diol epoxide DNA adducts; 2) smoking status by measurement of plasma cotinine; and 3) several antioxidant vitamins measured by reverse-phase HPLC (retinol, tocopherols) or spectrophotometry (ascorbic acid). We have recently developed sensitive immunoperoxidase methods for quantitation of PAH-DNA, 8-hydroxydeoxyguanosine (8OHdG) and 4-amino biphenyl (4-ABP)-DNA. For this reason, additional funds are requested for analysis of PAH-DNA and 8OHdG in oral cells and 4-ABP-DNA in exfoliated bladder cells by immunoperoxidase staining. In addition, we have data suggesting that serum levels of antioxidant vitamins have a protective effect on mononuclear cell PAH-DNA adducts only in smokers who lack the glutathione S-transferase Ml gene. Thus, we propose to also genotype subjects for GSTM1 and GSTT1, transferases deleted in a large percentage of the population. The demonstration that DNA damage can be modulated in target tissues for smoking induced cancers by dietary antioxidants will provide important information justifying their use as intermediate biomarkers in intervention studies.